The technique is known of superimposing a plurality of laser beams to increase the laser output.
As related techniques, Patent Literature 1 discloses an image forming apparatus. The image forming apparatus disclosed in Patent Literature 1 includes a housing which covers an optical system from a laser beam source to an oblique mirror, and a cooling fan which cools the housing.
Also, Non-Patent Literature 1 discloses a fiber array system which includes a seed laser, a fiber splitter, phase shifters, fiber amplifiers, and a fiber array transmitter. In Non-Patent Literature 1, the fiber splitter splits the laser beam received from the seed laser. The phase shifter shifts the phase of the split laser beam. The fiber amplifier amplifies the laser beam received from the phase shifter. The fiber array transmitter focuses a plurality of laser beams received from the fiber amplifiers for a target.